FAQ

On Jan 13, 2011 2:24 AM, "Uri Guttman" wrote:
"sw" == shawn wilson <ag4ve.us@gmail.com> writes:
subs in perl ALWAYS return something, either the value from return or
the last evaluated expression.
sw> What do you mean by this?

sw> sub nothing {
sw> my $something = 5;
sw> if ( $something == 5) {}
sw> }

sw> ... will return 'undef' and not 5 or anything else, right?

from perldoc perlsub:

A "return" statement may be used to exit a subroutine, optionally
specifying the returned value, which will be evaluated in the
appropriate context (list, scalar, or void) depending on the context of
the subroutine call. If you specify no return value, the subroutine
returns an empty list in list context, the undefined value in scalar
context, or nothing in void context. If you return one or more
aggregates (arrays and hashes), these will be flattened together into
one large indistinguishable list.

If no "return" is found and if the last statement is an expression, its
value is returned. If the last statement is a loop control structure
like a "foreach" or a "while", the returned value is unspecified. The
empty sub returns the empty list.

i never said subs return something useful but something is always
available to the caller on the stack. this is one (of many) reasons i
say to (almost) always use explicit returns. it guarantees you know what
you are returning, it tells the reader what is being returned and it
avoids bugs. one classic bug is some code that returns the last
expression and someone adds code after that breaking the return. another
bug is when the last statement is some compound thing like if/else and
it may return the right thing but it is hard to tell what is going
on. and as the docs say a loop control will be unspecified in what it
returns. so use explicit return statements to avoid all of these
issues. simple and important.

there are some special cases where no return statement may be better. i
won't go into those now.
I dig what you're saying about always using return. However I don't (have
never used / seen) a case where a sub returns last expression. An example
maybe?

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